"THERE’S A SUCKER born every minute.” That quotation, widely attributed to P.T. Barnum, originally referred to deceptive carnival sideshow attractions, but it’s just as relevant to online scams—in particular, Facebook scams—today. None of the common Facebook frauds—the “Facebook dislike button,” the “stalker tracker” (which purports to tell you who’s visiting your profile), and “watch this…